1. Field of the Invention
The present invention relates to a method of manufacturing a toner according to a toner used for electrophotography, a toner obtained by a method thereof, a one-component developer, a two-component developer, a developing device and an image forming apparatus.
2. Description of the Related Art
An image forming apparatus employing an electrophotography farms an image by a charging step, an exposure step, a developing step, a transfer step, and a fixing step. At the charging step, the surface of a photoreceptor is uniformly charged by a charging section. At the exposure step, a laser beam is irradiated by the exposure section to the charged photoreceptor surface and an electrostatic latent image is formed. At the developing step, the electrostatic latent image on the photoreceptor is developed by a developing section and a toner image is formed on the photoreceptor. At the transfer step, the toner image on the photoreceptor is transferred onto a recording medium by a transfer section. At the fixing step, the toner image transferred onto the recording medium is heated by a fixing section and the toner image is fixed on the recording medium.
To realize energy saving of the image forming apparatus at the above fixing step, development of a low temperature fixation toner in which a binder resin whose softening point is low is used and which is fixable at a relatively low temperature, is in process. However, by using the binder resin whose softening point is low, preservation stability of a toner decreases and a toner aggregation may be generated.
Therefore, in order to enhance the preservation stability of the toner, a surface modification treatment for coating the surfaces of toner core particles with a coating material has been performed. By coating the toner core particles and manufacturing a toner, the toner aggregation is able to be suppressed.
Japanese Examined Patent Publication JP-B2 5-10971 (1993) discloses as a method of the surface modification treatment, a method that a mechanical stirring force is applied to powder particles by a rotary stirring section such as a screw, a blade, or a rotor to fluidize the powder particles in a powder flowing passage, a liquid is sprayed from a spray nozzle to the powder particles in a fluid state, and the surfaces of the powder particles are coated by a coating material contained in the spray liquid. According to the method described in JP-B2 5-10971, adhesiveness between the coating material and the powder particles is able to be improved and time required for the surface modification treatment is able to be shortened.
Further, Japanese Unexamined Patent Publication JP-A 3-293676 (1991) discloses a method of manufacturing a microcapsule in which resin particles and fine inorganic particles adhere to the surfaces of inner core particles and the resin particles are dissolved with a solvent to form a coating layer on the surface of the inner core particle. According to the method described in JP-A 3-293676, after forming the coating layer on the surface of the inner core particle with the treatment using the solvent, a microcapsule is obtained by drying and removing.
Since, however, a coating material in a spray liquid is in a state of aggregation by a method described in JP-B2 5-10971, there is a problem that an aggregation thereof adheres to the surface of a powder particle without disintegration so that thickness of a coating material layer formed on the surface of the powder particle is non-uniform. Additionally, since a large quantity of a dispersant is contained in the spray liquid so as to disperse the coating material, there is also a problem that a dispersant remains inside and on the surface of the coating material layer.
Further, there is also a problem that since the spray liquid on a particle of a coating material detaches or evaporates easily, the coating material layer is not sufficiently formed. On the other hand, when an amount of the spray liquid is increased to solve the problem, the spray liquid is retained in the manufacturing apparatus so that the powder particle adheres to a wall surface inside the manufacturing apparatus, and the yield is lowered.
Further according to the method described in JP-A 3-293676, the solvent which has dissolved the resin particles becomes hard to vaporize. Thereby, the aggregate of the inner core particles are generated or the inner core particles adhere to an inner wall surface of the manufacturing apparatus. As a result, the yield is lowered. Moreover, some type of solvent may even dissolve the inner core particles. When the inner core particles are dissolved, an additive such as wax inside the inner core particles is fixed or exposed on the surfaces of the inner core particles, and the preservability or the like of the microcapsule is lowered.